Extract string when from dynamic input where part of the string may not exists-CodePudding

Lets assume I have a string

Abc=cde&efg

This formula gives me three groups

(.*=)(.*)(&.*)

But what if input string is dynamic and &efg may exists or not?
When it doesn't above formula will give me nothing. I need to use this regex in golang and I would like to do it with one regex (if it is possible) without splitting string with &.

CodePudding user response：

You can use

^(.*=)(.*?)(&.*)?$

See the regex demo.

Details:

^ - start of string
(.*=) - Group 1: any zero or more chars other than line break chars as many as possible and then a = char
(.*?) - Group 2: any zero or more chars other than line break chars as few as possible
(&.*)? - Group 3 (optional): a & and then any zero or more chars other than line break chars as many as possible
$ - end of string.